Vehicles, such as automobiles and trucks for example, include a differential and axle assembly, sometime colloquially referred to as a drive module. This assembly is connected to the vehicle engine by a drive or prop-shaft having a mass. The prop-shaft transmits rotational energy (torque) developed by the vehicle engine to the differential and axle assembly, which in turn transmits the rotational energy to the wheels. In a rear-wheel drive vehicle, the prop-shaft directly couples the differential and axle assembly to the vehicle's transmission. In an all-wheel or four-wheel drive vehicle, additional components may also be included, such as a power take-off unit for example.
The prop-shaft imparts a mass load to the differential. More specifically, the prop-shaft is attached to a pinion gear of the differential through a pinion flange. In addition to applying rotational/torsional loads from the engine, the mass of the prop-shaft imparts a downward load to the pinion gear. Further, driveline systems often include dampers that may counteract a sympathetic vibration response triggered by engine firing excitation. Typically, the damper is mounted on the driveshaft or the pinion flange. The addition of the damper to the driveline system mass can force even more costly bearing and pinion size upgrades in order to maintain performance with the additional load. In order to address the loading of the prop-shaft, the pinion is made of a robust material that typically adds even more weight to the differential assembly. The type of material used to form the pinion gear increases manufacturing costs and also provides a negative impact on fuel economy.
Accordingly, it is desirable to provide a differential and axle assembly having a pinion gear that may possess a reduced weight yet still be designed to accommodate the rotational/torsional loads provided by the engine.